Actuator assemblies are used in myriad devices and systems. For example, many vehicles including, for example, aircraft, spacecraft, watercraft, and numerous other terrestrial and non-terrestrial vehicles, include one or more actuator assemblies to effect the movement of various control surfaces or components. In many applications, the actuator assemblies include power drive units, such as motors, that are configured to receive a source of drive power to move an actuator, and thus the control surfaces or components, to a commanded position. When the control surfaces or components reach the commanded position, the source of drive power may be removed. Thus, many of the actuator assemblies that are used include what is sometimes referred to as a no-back device. The no-back device is configured to hold the actuator in position against the load once the actuator has moved the control surface or component to the commanded position.
The types and configurations of no-back devices that are included in actuator assemblies vary. One particular type of no-back device that is used is a permanent magnet device. This type of device typically includes one or more permanent magnets that prevent rotation of the power drive unit when the source of drive power is removed. Another type of no-back device is a multi-rotor friction brake. Although these types of no-back devices, as well as the various other device types that are currently known, are generally safe, reliable, and robust, these devices do suffer certain drawbacks. For example, the presently known devices permanent magnet devices supply a continuous magnetic force against power drive unit rotation, in at least one rotational direction, that the power drive unit may need to overcome each time it is supplied with drive power. As a result, the size of the power drive unit may be larger than what is needed to move the load alone, in order to overcome this magnetic force, which can increase overall actuator and system size, weight, and costs. Moreover, the friction type devices can wear relatively quickly, resulting in the need to replace the devices, which can increase overall costs.
In addition to the above, many actuators include an interposing element, such as a gear assembly or screw, between the power drive unit and the actuator. In many instances, it is desirable to physically implement an actuator that has a relatively small size and low weight. In the past, these goals have been met by using a relatively small electric motor that rotates at a relatively high rotational speed, and then including some type of gear reduction to increase the output torque of the actuator.
Hence, there is a need for a no-back device that does not supply force against drive unit rotation, and/or is less prone to wear, and/or does not result in increased overall actuator assembly and system size, weight, and/or costs. There is also a need for an actuator assembly that includes a small, high speed motor with sufficient gear reduction that has a relatively small space envelope and/or relatively smaller weight as compared to known actuator assembly configurations. The present invention addresses at least one or more of these needs.